Psycho (1960)

While most twist endings age horribly, Psycho’s big surprise remains creepy to this day. When clients start getting killed off at the super sketchy Bates Motel, all signs point to Mrs. Bates, the aged owner scarcely seen around the lodging, being a crazed killer -- which, I guess, is partially true. Mrs. Bates might be dead, but her son Norman has developed a split personality and one of those voices in his head belongs to his mother. This dark side encourages him to dress up like a sweet old lady and kill, kill, kill!